cryptsetup 2:1.0.4-8ubuntu2 (amd64 binary) in ubuntu feisty

 Since kernel 2.6.4, encrypted filesystem support is provided by the device
 mapper target dm-crypt. This utility provides a command-line interface for
 configuring this facility. It has integrated support for LUKS.
 .
 cryptsetup is backwards compatible with the on-disk format of cryptoloop,
 but also supports more secure formats. This package also includes support
 for automatically configuring encrypted devices at boot time via the config
 file /etc/crypttab. When combined with newer versions of the debian
 initrd-tools and standard debian kernels, cryptoroot is also supported.
 .
 For information on how to convert your system to use encrypted filesystems
 please read /usr/share/doc/cryptsetup/CryptoRoot.HowTo.